Direct-positive photographic process



19,1952 c. J. NOWAK EI'AL 2,607,684.

'. DIRECT-POSITfVE PHOTQGRAPHIC PROCESS Filed Sept. 24, 1949 IMAGE EXPOSURE /UNHARDENED EMULSION LAYER CONTAINING A LIGHT-ABSORBER FRI-EXPOSED .sTRATuM 0F UNHARDENED EMULSION EXPOJED NEGATIVE AREA :-PRE- EXPOSED STRATUM TANNING DEVELOPMENT A ram/5p GfLAT/N NEGATIVE 15 g h H "I UNHARDENED EMULSION A TAN/YEP GELAT/N POSITIVE CHESTER J. NOWAK RALPH S COLT INVENTORS ATTORNEY d3 AGENT Patented Aug. 19, 1952 rem orslos 4 'smsemesmvs Pantomime i.

PROC

Chester J; Nowak and Ralph S. Colt; Rochester, N. Y.; assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application September 24, 1949, serial No; 117,614

7 Claims.

This invention relates to the production of photographic images by a direct-positive process which images are particularly useful in color photography as imbibition dye transfer matrices.

The conventional method of producing dyetransfer matrices involves the production of three" color-separation, negatives and forming three matrices therefrom which are subsequently used in the transfer of three subtractively colored dyes to a single" imbibiti'oh blank. In this process it is desirable to prepare the matrices by a direct positive process thereby eliminating the step of preparing thejinterme'diat'e negatives. "Several processes have been suggested'for this purpose, for example, 'a ,gelatino-silver halide emulsion ay b exposed'to an aspect of a colored subject and after development of the exposed element, the exposed emulsion area is removed by means of a peroxide bleach bath whichsolubiliz es the'emulsion in the region of the silver image. Ori'e difficulty of this process, among others, lies in the fact that the process requires the use of a heavily ,dyed emulsion layer in orderv to restrict the color separation exposure to the outer surface of the emulsion layer. Since it is necessary to exposethrough to the base in the light region and since the dyed emulsion'res'ists such exposure, the element has such low speed that the printing time is obj ectionably long."

Similarly, in cases where it is desirable to reproduce or duplicate black and-white images, for example, in preparing duplicate negatives, an appreciable saving in time and materials as wellas an improvement in quality can be effected if the intermediate step of producing a positive can be dispensed with.

outer stratum of emulsion of a photographic element having a support usually a transparent film carrying two strata of gelatino-silver halide emulsion separated by a water-soluble colloid stratum, the stratum adjacent the support containing uniformly exposed silver halide, and after exposure, simultaneously developing a negative silver image in the outer stratum and apositive silver image in'the stratum adjacent the support leaving soluble colloid separating the silver images, and thentreating withwarm water to remove the outer stratum and colloid stratum thereunder to leave a direct-positive image on the support. More particularly, when our process is applied to the production of directpositive relief images, the objects of our invention in general are accomplished by image wise exposing the outer stratum of a sensitive element having a support carrying a fogged and substantially unhardened gelatino-silver. halide emulsion stratum' adjac'ent the support and an unexposed substantially unhardened gelatinosilver halide emulsion stratum outermost, leaving a stratum of unexposed soluble emulsion separating the two exposed strata, then developing the element in a tanning developer composition to simultaneously form positive and negative tanned images separated by soluble emulsion and then removing the outer tanned "One object of our process is to provide a sim'- H plified direct-positive process of producing dye transfer matrices as wellas silver images. Another object is to providevariou's methodsan'd materials useful for 'parryin'g out ourprocess. Another object is to provide a variation of our process by which matrices may be'correcte'd to EXAMPLE 1 A sensitive photographic film including a substantially unhardened panchromatic gelatinosilver halide emulsion layer on a cellulose ester support is provided. The emulsion layer should contain a light absorber such as a'dye or carbon black. The emulsion layer is preferably first uniformly exposed from the base side so as to 3 obtain a pre-exposed stratum of emulsion adjacent to the support or this exposure can be made subsequent to the image exposure. It is within this region that the direct positive matrix will be formed. The film appears at this point as shown in the first stage of the drawings wherein layer I is a transparent support of a cellulose ester, for example, cellulose acetate carrying the unhardened emulsion layer II, the stratum I 2 of which has been exposed. The element is then exposed to the positive I3 which may be a positive subtractively colored transparency although negative color films as well as black-and-white transparencies, both positive and negative may be used. Since colorseparation matrices are desired when the positive I3 is a color transparency, the exposure light is suitably filtered, for example, using a blue, green or red filter. The duration and intensity of exposure are so adjusted that a stratum of unexposed emulsion remains separating the exposed areas as represented in the second stage of the drawings wherein the emulsion layer II is shown as now containing the exposed stratum I2, the exposed negative area [3 and a stratum I4 of unexposed emulsion separating the exposed areas I2 and I3.

The element is then developed'for 2 minutes at 68 F., or longer depending on whether lower contrast is desired in the final positive relief image, in a tanning developer of the following composition:

Solution A Grams Pyrocatechol 2.5 Pyrogallol 2.5 Potassium metabisulfite 3 Potassium bromide 1 Water to make 1 liter.

Solution B Grams Sodium hydroxide 5 Water to make 1 liter.

Mix 1 part of Solution A, 1 part of Solution 13, 2 parts water and use immediately after mixing.

The result is to obtain simultaneously silver and tanned gelatin images of the character reprepresented in the third stage of the drawings wherein emulsion layer II is shown as containing a silver and tanned gelatin negative image in area I3 and a silver and tanned gelatin positive image in area I5. Area I6, comprising unhardened emulsion, separates the images in areas l3 and I5. Subsequently, the element of the third stage of the drawings, is treated with a dilute acetic acid stop bath, 0.5% acetic acid is satisfactory, and then immersed in or treated with hot water at about 130 F. which causes the emulsion area IE to melt and dissolve, thereby allowing the tanned image [3 to be removed. The appearance of the resultant direct positive matrix film is shown in the last stage of the drawings according to which the support It now carries the direct-positive relief image I5. The element may be further washed with hot water to remove the last traces of unhardened emulsion, then hardened in a hardening bath such as the usual acid hardening fixing bath, and if desired, the silver image in the colloid relief may be removed by conventional methods involving bleaching the silver and fixing out.

It is desirable to incorporate an absorber such as carbon black in the initial emulsion inbrder to prevent joining of the image and fiash exposed EXAMPLE 2 fast substantially unhardened panchromatic emulsion of a well-known negative type containing no absorber. The film is given a uniform flash exposure from the base side so as to expose a stratum'but not necessarily all of the emulsion adjacent to the support, or the lower emulsion may previously have been made developable by chemical or exposure methods. An exposure of approximately 10 seconds at 8 feet from a 60-watt lamp through a red color-separation filter is generally satisfactory. The'film is then exposed by contact or projection from the side opposite the support through a suitable color transparency using the appropriate color separation filter. With conventional tri-color filters, for example, Nos. 29, 61 and 47, approximately 0, 40 and 120 seconds exposure at 8 ft. from 2. 60-watt lamp are sufiicient for the red, green and blue colorseparation exposures, respectively. The filter numbers given refer to filters having the characteristics shown on pages 36, 50 and 42, respectively, of the publication Wratten Light Filters, 14th edition, 1936, published by Eastman Kodak Company. The exposed filmis then developed as in Example 1 in the tanning developer solution. Following a short rinse in the acetic acid stop bath, the film is washed in hot water to dissolve the unexposed emulsion stratum and remove the tanned negative image. The resultant direct-positive color-separation matrix is then hardened and fixed, and if desired, the silver image is removed from the colloid relief in a well-known manner. The matrix is then ready for use in a dye-transfer, process involving the usual steps of dyeing up the matrix in an acid dye solution and transferring the vimbibed dye to the imbibition blank. 'In this process, instead of flashing or fogging the lower-most, stratum of emulsion, a comparable eifectds obtained if an unhardened pre-fogged emulsion is coated, or fogged after coating on.a support and overcoated with an unhardened panchromatic emulsion. Also, the initial sensitive element may be devoid of the light absorber inwhich case we use a slow blue sensitive emulsion next to the support the outer emulsion being a fast panchromatic emulsion. Useful results are obtained by using ultraviolet light for uniformly flashing the slower layer and to limit penetration ofthe exposure into the emulsion. 1 Q j V In case it is desired to introduce a. correction into the matrix toc'ompensate-for-the defi- Inthis case apart of the uniform exposure from the base side is replacedby the exposure through the transparency and the filter selected for color correction. The-following table providestypical exposure times for three matrices using, conventional red; green filters as color-correction filters.

Cyan matrix 'Support side H Seconds Uniform flash No; 29 filter 4 l'hro'ugh original 29' filter 18 Emulsion sidet Through original 29 filter l Ma enta mat'rz'zi" surrounds Seconds Uniform flash No. 29 fi1ter;. 1. 4 1 Through original-'29 filter"-. 18 Emulsion 'side' H Through original 61.n1tr 40 Yellowv matrix Support sidev Seconds Uniform flash No. 61 filter 7 Through original 61 filter '72 Emulsion side- 7 Through original No. 47+29 120 After the color correction exposure has been made, the element is processed as described in the above examples employing tanning development and hot water washing steps.

While the mechanism of our process is not thoroughly understood, the following tentative explanation is given. Referring to the figure of the second stage of the drawings, it will beseen that the film at this stage contains latent images in areas 12 and. [3. It might be expected, as happens to be the case, that in the subsequent tanning development step, a tanned image would be produced in area 13 distributed in the layer as shown. Also it might be expected that a uniformly tanned image would be obtained throughout area l2. However, it appears that because of exhaustion effects produced by development of area [3, in area [2 less tanning is produced in those parts adjacent to the more heavily exposed areas of image area I3, while tanning is not impeded in the vicinity of those regions of area [3 having less exposure. Consequently, the tanned image produced in area 12 has the characteristics shown in area l5 of the third stage of the drawings. Since untanne'd emulsion separates areas 13 and 15, the subsequent hot Water wash solubilizes this emulsion and permits removal of the overlying tanned gelation negative. When the auxiliary color correction exposure through the support has been employed, the characteristics of the final relief image are of course determined both by the auxiliary exposure and the exhaustion effects produced by development of the negative image in area I3.

The principal advantages of our process now become apparent. The fact that our process produces matrices in a direct-positive manner eliminates appreciable materials, and effects considerable savings in processing time. Quality of the matrices is improved partly because fewer steps are required. Compared to the direct-positive peroxide-bleach process, we obtain all of the advantages of a faster printing film.

EXAMPLE 3 When adapting our process to the production of duplicate silver images for example, duplicate negatives, we take a film having a support carrying two gelatino-silver halide'e'mul sions of" the customary hardness, the emulsion adjacent the support is an inherently blue-sensitive emulsion and the other is preferably a long-scale ortho or panchromatic emulsion. The two emulsions are separated by a thin soluble colloid interl'ayer, for example, of unhardenedgelatin or other warm water soluble colloid- Theemuls-ion adjacent the support may havebeen fogged'prioror subsequent to coating; Image-wiseexposureof the outer emulsion under asuitable silver negative (or positive) is effected, followed by development in an ordinary black-and-white developer. Exhaustion effects'of development of the image in the outer layer control development of the directpositive image in the layer adjacent the support, and after development, the outer emulsion and soluble colloid thereunder are removed with Warm water leaving the-duplicate silver image on the support. in casethe uniform-exposure of the stratum of thelower layer is carried out by a flash exposure through the base, ultraviolet light may be used for this purpose and for the imagewise exposure of theother layer, green or yellow light is used having no effect on any unexposed emulsion of the bottom layer.

Here and in the appended claims we mean the Word stratum to include not only a discrete layer positioned among or adjacent to layers of other kinds but also a uniform. area having some character different thanthe single layer of which it Was-originally an integral part..

It is to be understood that the, disclosure herein is by Way of example and that we consider asfincluded in our invention all modifications and equivalents falling within the scope of the appended claims.

1. The method of making a direct-positive photographic relief imagein a photographic element having a support substantially impermeable to photographic developing solution carrying a fogged substantially unhardenedgelatino-silver halide emulsion stratum and an unexposed substantially unhardenedgelatino-si'lver halide emulsion stratum over said fogged stratum, which comprises image wise exposing said unexposed emulsion leaving a stratum of unexposed: soluble emulsion separating the fogged stratum and the imagewise exposed stratum, developing. the exposed.- element in a tanning developer composition to simultaneously form a positive silver and tanned gelatin image adjacent the support, a negative silver and tanned gelatin image in the region of the image exposure, and a stratum of soluble emulsionseparating said tanned images, thereafter, removing said. tanned negativeimage and soluble emulsion by treatment with hot water leaving a positive relief image on said support. w

' -2.-The method of: making: a direct-positive photographic relief image which comprises uniforinly exposing to light a stratum of substantially unhard'ened gelatino-s'ilve'r'halide emulsion coated on a transpare" I support substantially impermeable to photographic developing solution fro-r nthe support-side, image=wise exposing another stratum of substantially unhardened gelatin-silver halide emulsion from the side opposite the support leaving unexposed soluble emulsion separating said exposed strata, developing the exposed element in a tanning developer composition to simultaneously form a positive silver and tanned gelatin image adjacent the support, a negative silver and tanned gelatin image in the region of the image exposure, and

a stratum of soluble emulsion separating said' tanned images, thereafter removing said tanned negative image and soluble emulsion by treatment with hot water leaving a positive relief image on said support. p

3. The method of making a direct-positive photographic relief image which comprises uniformly exposing to light from the support side a stratum of a single substantially unhardened gelatino-silver halide emulsion layer containing a light-absorber coated on a transparent support substantiallyimpermeable to photographic developing solution, then image-wise exposing another stratum of the emulsion layer from the side opposite the support leaving an unexposed stratum of soluble emulsion separating said exposed regions, developing the exposed element in a tanning developer composition to simultaneously form a positive silver and tanned gelatin image adjacent the support, a negative silver and tanned gelatin image in the region of the image exposure, and a stratum of soluble emulsion separating said tanned images, thereafter, removing said tanned negative image and soluble emulsion by treatment with hot water leaving a positive relief image on said support.

4. The method of making a direct-positive photographic relief image in a film having two substantially unhardened gelatin-silver halide emulsion layers superposed on a transparent support substantially impermeable to photographic developing solution, which comprises uniformly exposing to light an emulsion stratum adjacent the support without exposure of said outer emulsion layer, image-wise exposing an outer stratum of said outer emulsion layer leaving unexposed soluble emulsion separating the exposed strata, developing the exposed element in a tanning developer composition to simultaneously form a positive silver and tanned gelatin image adjacent the support, a, negative silver" and tanned gelatin image in the region of the image exposure, and a stratum of soluble emulsion separating said tanned images, thereafter,

removing said tanned negative image and soluble emulsion by treatment with hot water leaving a positive relief image on said support.

5. The method of making a direct-positive photographic relief image in a film having two substantially unhardened gelatino-silver halide emulsion layers on a transparent support substantially impermeable to photographic developing solution, the outermost emulsion layer having appreciably greater sensitivity, which comprises uniformly exposing to light an emulsion stratum adjacent the support without exposure of the outermost emulsion layer, imagewise exposing an outer stratum of said outermost emulsion layer leaving a stratum of unexposed soluble emulsion separating the exposed regions, developing the exposed element in a tanning developer composition to simultaneously form a positive silver and tanned gelatin image adjacent the support, a negative silver and tanned gelatin image in the region of the image exposure, and a stratum of soluble emulsion separating said tanned images, thereaftenremoving said tanned negative image and soluble emulsion by treatment with hotwater leaving a positive relief image on said support.

6. The method of making a direct-positive photographic relief image in a film having two substantially unhardened panchromatic gelatino-silver halide emulsion layers superposed on a transparent support substantially impermeable to photographic developing solution, the outermost emulsion layer having appreciably greater sensitivity than the other emulsion, said other emulsion containing a light absorber, which comprises uniformly exposing to light an emulsion adjacent the support without exposure of the outermost emulsion layer, imagewise exposing an outer stratum of said outermost emulsion layer leaving unexposed soluble emulsion separating the two exposed regions, developing the exposed element in a tanning developer composition to simultaneously form a positive silver and tanned gelatin image adjacent the support, a negative silver and tanned gelatin image in the region of the image exposure, and a stratum of soluble emulsion separating said tanned images, thereafter, removing said tanned negative image and soluble emulsion by treatment with hot water leaving a positive relief image on said suppor '7. The method of making a direct-positive photographic relief image which comprises uniformly exposing to light a stratum of substantially unhardened gelatino-silver halide emulsion layer coated on a transparent support substantially impermeable to photographic developing solution from the support side, exposing another stratum of substantially unhardened gelatinosilver halide emulsion from the side opposite the support to a color-separation image of a colortransparency, in registry exposing said sensitive element from the support side through said transparency to a wavelength of light improperly absorbed by images of said color transparency leaving some unexposed soluble emulsion separating said color-separation image region from other exposed regions, developing the element in a tanning developer composition to simultaneously form a color-corrected positive silver and tanned gelatin image adjacent the support, a negative silver and tanned gelatin image outermost, and a stratum of soluble emulsion separating said tanned images, removing said tanned negative image and soluble emulsion by treatment with hot water leaving a color-corrected positive relief image on said support.

CHESTER J. NOWAK. RALPH S. COLT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,993,576 Troland Mar. 5, 1923 2,218,229 Carroll Oct. 15, 1940 FOREIGN PATENTS Number Country Date 716,428 France Oct. 6, 1931 OTHER REFERENCES Ricketts, British Journal of Photography, June 5, 1914, page 446. 

1. THE METHOD OF MAKING A DIRECT-POSITIVE PHOTOGRAPHIC ELIEF IMAGE IN A PHOTOGRAPHIC ELEMENT HAVING A SUPPORT SUBSTANTIALLY IMPERMEABLE TO PHOTOGRAPHIC DEVELOPING SOLUTION CARRYING A FOGGED SUBSTANTIALLY UNHARDENED GELATINO-SILVER HALIDE EMULSION STRATUM AND AN UNEXPOSED SUBSTANTIALLY UNHARDENED GELATINO-SILVER HALIDE EMULSION STRATUM OVER SAID FOGGED STRATUM, WHICH COMPRISES IMAGE-WISE EXPOSING SAID UNEXPOSED EMULSION LEAVING A STRATUM OF UNEXPOSED SOLUBLE EMULSION SEPARATING THE FOGGED STRATUM AND THE IMAGE-WISE EXPOSED STRATUM, DEVELOPING THE EXPOSED ELEMENT IN A TANNING DEVELOPER COMPOSITION TO SIMULTANEOUSLY FORM A POSITIVE SILVER AND TANNED GELATIN IMAGE ADJACENT THE SUPPORT, A NEGATIVE SILVER AND TANNED GELATIN IMAGE IN THE REGION OF THE IMAGE EXPOSURE, AND A STRATUM OF SOLUBLE EMULSION SEPARATING SAID TANNED IMAGES, THEREAFTER REMOVING SAID TANNED NEGATIVE IMAGE AND SOLUBLE EMULSION BY TREATMENT WITH HOT WATER LEAVING A POSITIVE RELIEF IMAGE ON SAID SUPPORT. 